1. Field of the Invention
The invention relates to an electrically-heated ice dam remediation apparatus for preventing or ameliorating the formation of ice dams on roofs; in particular to a device powered by pholtovoltaic cells directly connected electrically to a heat tape or wire cable arranged along the roof edge in an orientation which creates and maintains open channels in the ice or snow along the eaves, permitting water to drain off the edge of the roof.
2. Description of the Prior Art
In areas which experience significant amounts of snow, the formation of ice dams on roofs is a common problem. After a snowstorm, snow on the roof tends to melt in relatively warm areas of the roof, causing water to run down the dip or slope of the roof towards the eave. The runoff water tends to freeze along the eave, creating an ice dam, an irregular sheet or ridge of solid ice which increasingly obstructs further flow of water and so leads to accumulation of still more ice along the edge of the roof and particularly in shaded areas and in angles of the roof. In this way ice dams many inches thick may be created over the course of several snowstorms. Such ice dams are subject to alternate freezing and thawing, which physically damages the roof surface and the eaves and which also creates gaps and cracks through which water can flow under the shingles or other roof surface material and into the building. In addition, ice dams spawn icicles, which often grow to sizes that present a danger to passersby when the icicles break loose and fall.
Ice dams form most persistently in roof areas which are partially or completely shaded from direct sunlight. In the Northern Hemisphere, north- and east-facing roof surfaces and edges are most subject to the formation of ice dams; as are roof surfaces which are permanently shaded from direct sunlight by other structures, trees or the like.
Electrical heat tape or wire cable powered by house current is commonly used to heat portions of the roof subject to ice dam formation. Typically, 110 volt AC power is applied to heat tape or wire cable installed so as to cover a substantial portion of the entire roof edge; such installations must be grounded (and so require installation by a certified electrician). In addition to the fire and shock hazard posed by such arrangements, they use substantial amounts of costly electrical power, in part because they are typically powered up continuously, day and night, even though night-time temperatures are often so low that it is not possible to melt snow and ice even with heat tape or wire cable. Power usage for such systems on residential structures often exceeds 1000 Kw-hrs per month.
Some installations of this general type may use low-voltage heat tape or wire cable powered by a transformer, which in turn uses 110 volt house current. See, for example, U.S. Pat. No. 7,071,446 B1 (Bench). But, such arrangements still use expensive purchased electric power; they typically require installation by licensed electricians, and in addition they may require voltage or temperature regulation control systems which, along with the transformer, further add to the installed cost.
A number of patents disclose a variety of solar-heated devices which are intended to create and maintain open slots, tunnels or channels through ice dams, and so prevent or ameliorate the problems caused by ice accumulation. See, e.g., U.S. Pat. No. 4,333,444 (Sell); U.S. Pat. No. 4,252,183 (Ricciardelli) and U.S. Pat. No. 4,261,417 (Tingley). Such devices are not electrically powered but instead depend upon conduction of solar heat, usually via a metal structure, directly to the area of ice damming. As a result, they are unsuitable (or at best only marginally usable) for shaded roof areas which are most subject to ice dam formation. And although heat pipes can be used to conduct heat to an area of ice dam formation, as in Tingley '417, such heat pipes typically require a straight run (no bends or corners) and have very limited lengths.
U.S. Pat. No. 6,093,885 (Takehara) describes a photovoltaic power generating system in which snow falling on the photovoltaic cells themselves is said to be melted off using electrical heat. The electrical heat is generated by applying a voltage from an external power source to the solar cells themselves. Because of this arrangement, snow melting normally must be done at night with this device; and substantial electrical power from some source other than the photovoltaic cells themselves is required. Moreover, situating photovoltaic cells directly on a roof edge area subject to ice dam formation would damage or destroy the cells. U.S. Pat. No. 5,368,654 (Bergevin), which teaches modifications to a photovoltaic structure intended to trap heat energy directly, would suffer from this drawback as well.